I could use a little advice, I have been distilling for over ten years, rum and sour mash mainly. I use natural cane sugar and untreated washed cracked corn, distillers yeast and yeast nutrient (UJSM recipe) in the recommended amounts. Everything was just rosie until my last two runs, I dumped the first 150 ml then collected about 2500 ml in 100 ml increments in 1/2 pint ball jars with plastic lids, as is normal. After making cuts (I only Keep hearts) I was distracted and and left the product in the cutting jars for several weeks, this happened again on the next run. I noticed a small amount of a black particulate, residue, sediment in the cutting jars. I then checked the storage jars from the earlier run and found this sediment also. Can anyone tell me about the black stuff?

The sulfur can come from any number of sources. In my case it's usually hydrogen sulfide from the bacteria in the aquifer (I have well water). I can actually smell it sometimes in the late spring and summer. Smells like rotten eggs. Although the odor is offensive, it's harmless. Anyway the hydrogen sulfide apparently reacts with the copper and somehow you end up with copper sulfide.

Also, you can get some sulfur (sulfur dioxide) from your cane sugar. Perhaps you changed brands? Or the manufacturer/distributor changed its source? Could be any number of things.

Or perhaps it's time to acid wash some of the copper in your system. A little citric acid, lemon juice, etc. with some water does wonders.

I guess it's possible that it has always been there, but your process of diluting early prevented its formation (crystallization) ... especially if there's any chlorine in the water you're using to dilute with.

My chemistry pretty much sucks once I'm beyond the basics ... but, I do know that a little chlorine will cause copper sulfide crystals to precipitate. Many homes in my area have these chlorine traps (I believe that's what they call them ... they look like basket filters) but you can add chlorine tablets to them. The idea is to eliminate the copper sulfide close to the source to prevent particles and that occasional rotten egg smell. If you can isolate some of those particles and put them in a clear glass of pool water ... and they go away ... then you can be reasonably sure of what you're dealing with ... then work the problem backwards.

Sorry for so much hot air ... figured you'd prefer more info than not enough.

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